2023-2024 Respiratory Virus Season Is Likely Past Peak but Far from Over

After a late December surge, respiratory virus activity has been declining for weeks, with most indicators trending down. Weekly hospitalization rates for COVID-19, flu, and respiratory syncytial virus (RSV) declined through most of January.

However, respiratory disease activity remains elevated, and some flu activity indicators have increased again. Test positivity for flu rose nationally in late January and has leveled off since but continues to increase in parts of the country. Emergency department visits for flu have been going up in some areas of the county.

While the respiratory virus season is likely past its peak, it is definitely not over. There is still a lot of respiratory virus activity, so it’s not time to let our guard down.

Hospitalizations and deaths are below last season’s

As we saw last season, COVID-19, flu, and RSV account for a large proportion of hospitalizations for respiratory viruses during the fall and winter months. This season, flu and RSV illnesses started increasing later in the fall, which is more like what we typically saw before the pandemic.

This season’s peak in combined COVID-19, flu, and RSV hospitalizations was not as high as last season’s. And there were fewer reports of healthcare strain this season. Additionally, cumulative hospitalizations and deaths due to COVID-19 and flu are lower this season than they were at this time last season.

There’s still time to get your vaccines

This was the first season where vaccines were available for COVID-19, flu, and RSV. At this point in the season, vaccination uptake for COVID-19 and flu is slightly lower than last season, which means many people are missing out on this layer of protection against the most severe outcomes of these illnesses.

Twenty-two percent of adults have received the updated COVID-19 vaccine this season, including 42% of people 65 and older, who are among those at highest risk of severe disease. COVID-19 activity remains high, and getting vaccinated can protect you from severe illness, hospitalization, and death.

An estimated 48% of adults have received a flu vaccine this season. The timing of flu seasons is unpredictable, and in some years significant flu activity has lasted into May. The good news is, if you haven’t yet gotten your flu vaccine there is still time, so that you can reduce your risk of flu and its potentially serious outcomes if you do get sick.

Similar to flu season, RSV infections usually begin to increase in the fall and peak in winter. During the 2021-22 and 2022-23 seasons, the number of RSV cases started increasing as early as July. Early vaccination ensures protection from RSV by the time activity begins to rise in communities. At this point, 22% of adults 60 years and older have received an RSV vaccination. It is important for people 60 years and older to talk to their healthcare provider to see if RSV vaccination is right for them.

Reminder for healthcare providers: We’re out of the seasonal window for timely RSV vaccination of pregnant people in most areas of the country, which is recommended only through the end of January. Babies younger than 8 months, and some older babies, can still get protection against RSV with an immunization called nirsevimab. Most babies younger than 8 months do not need nirsevimab if their mother got an RSV vaccine.

Additional actions to protect yourself against respiratory viruses

Testing to determine the cause of respiratory symptoms can help inform recommendations about the most appropriate treatment. Tests, including at-home tests for COVID-19, can detect these respiratory viruses so patients can better understand their illness and take next steps. Prescription treatments are available for both COVID-19 and flu.

Other tools that can help prevent the spread of COVID-19, flu, and RSV include masking, physical distancing, washing hands, and improving airflow in the places where people live and work.

More info for data mavens: Two systems for tracking COVID-19 and flu hospitalizations

CDC tracks COVID-19 and flu hospitalizations in two different but complementary ways. When you’re diving into the details, it’s important to understand the differences. For example, some have noted that COVID-19 hospitalizations appear consistently higher in one system, but it looked like flu had a higher hospitalization rate in another. Let’s dig in.

The National Healthcare Safety Network (NHSN) collects reports from all U.S. hospitals on COVID-19 and flu-associated hospitalizations. NHSN hospital data are national and provide a broader geographic picture of hospitalizations in terms of total numbers. NHSN data provide overall counts of hospitalizations and only some limited patient information. Additionally, NHSN does not include data on RSV hospitalizations.

• NHSN shows that COVID-19 hospitalizations have consistently outpaced flu hospitalizations in terms of total numbers.

By comparison, the Respiratory Virus Hospitalization Surveillance Network (RESP-NET) collects data from acute care hospitals in select communities in multiple states where nearly 10% of the U.S. population lives.

RESP-NET collects detailed (but anonymous) data on a wide range of patient and clinical characteristics for laboratory-confirmed COVID-19, flu, and RSV hospitalizations. These data are used to calculate hospitalization rates by age and race/ethnicity. Additionally, RESP-NET data are used to analyze and conduct analyses to determine risk factors for severe outcomes, including ICU admission, mechanical ventilation, and death.

• RESP-NET shows that overall population-based flu-associated hospitalization rates topped COVID-19-related rates during the last week of December in areas where data is captured in RESP-NET. Among adults ages 65 years and older, who make up two-thirds of all COVID-19 hospitalizations, rates of COVID-19 hospitalizations remained higher than those for flu for all weeks.
• From RESP-NET, we know that COVID-19-related illness was the likely presenting complaint on admission for about 80% of older patients with COVID-19-associated hospitalizations.